Rhizospheric bacterial isolates of grass pea (Lathyrussativus L.) endowed with multiple plant growthpromoting traits.

Abstract

The main aim of this work was to examine the plant growth promoting, biocontrol activities and stress competency of grass pea rhizobacterial strains from Ethiopia. Serial dilutions were carried out to isolate rhizobacterial strains from the rhizosphere soil samples. The isolates were characterized for their plant growth promoting, biocontrolling and stress tolerance potential. The isolates that showed better performance in the tested parameters were identified by 16S rRNA gene sequencing. Among the isolates tested on Pikovskaya agar medium, 22 isolates that showed solubilization index of >2·41cm were selected for further screening tests. Isolate AAUGPR-53 identified as Enterococcus species, Enterococcus casseliflavus strain showed the highest phosphate solubilization index and indole-3-acetic acid production efficiency of 4·81±0·02 (μgml-1 ) and 56·55±0·45 (μgml-1 ), respectively. Sixteen (72·7%) of the isolates showed invitro antifungal inhibition against Fusarium oxysporum f. sp. lentis with isolates AAUGPR-92 and AAUGPR-91 identified as Enterococcus species, E. casseliflavus strain and Enterococcus gallinarum strain exhibiting the highest inhibition of 83 and 78%, respectively. Likewise, 68·2%, 91·30%, 45·5%, 77·3% and 100% of the isolates produced chitinase, protease, cellulase, HCN and NH3 , respectively. Most of the isolates showed good tolerance to the tested stress factors. The 16S rRNA partial sequencing of the rhizobacterial isolates proved their taxonomic position in the existing bacterial isolates. The results indicated that three strains, AAUGPR-53, 91 and 92, that showed maximum sequence identity (99%) to Enterococcus species, E. casseliflavus and E. gallinarum were recommended as microbial inoculants for trials under greenhouse and field conditions. This study illustrates an effective alternative to conventional fertilizers that may contribute to crop disease reduction. Our results provide a foundation for future research that will lead to identifying potentially useful biocontrol strains found in the rhizosphere of grass pea.